It requires the melting of the raw compound using oxyhydrogen flame and the crystallisation on the melted droplets to variety a cylinder. Graded 9 over the Mohs-hardness scale (graded one-ten), the resulting sapphire crystals are pretty much scratch-evidence and very tough, ensuring an unhindered vision all of the time. Functional https://www.watchesworld.com/top-10-dive-watches/